Welcome to the board.
First of I wouldn't tell her 'no', ever, for growling. Not least because you don't yet understand why she is growling in the first place and that;s what you will need to learn. This could be caused by pain, by poor socialising (good socialising depends entirely on the dedication of the breeder), the dog's temperament (which also depends totally on the quality of the breeder and the care they take to preserve the correct breed temperament - for example, she could be aggressive, or very fearful, both of which could cause growling). It souns like you had a good breeder though.
The reason you should never punish a dog for growling is because growling is he only way a dog will give a clear warning BEFORE it bites. In dog language, it is being polite and issuing a final warning. If you scold a dog for growling and teach it not to growl, it may well instead go straight for biting. This is not something you ever want to happen, not least because small children in particular can easily, and accidentally, aggravate even the sweetest dog to move towards biting. You always want that growl first as it is very important to know when a dog is reaching its limit, for whatever reason -- annoyance, pain, being startled, whatever.
As for finding out the source: my first inclination would always be to have her vet checked, very carefully.
If there's no medical reason for growling, then -- assuming this puppy came from a reputable, health nd temperament focused breeder, I would ring the breeer for advice. If there's a tempermant issue any good breeder is going to want this information. And more generally, whatever the concern, a good breeder will be more than happy to offer advice and support.
If this is behavioural or due to temperament, then the way to discourage it is to make being carried around something that is neither annoying or scary and is instead, really positive!
. That means not lifting the puppy only when you are taking it away for confinement as that very association may cause the growl now as it is unhappy. Instead you need to practice gently lifting her when you are not confining her. At first just sit on the floor and lift her to a lap, then try lifting her a little higher. Praise and treat, then set her back down so she can play. You will need to try this many times a day so there isn't a negative association with being lifted.
Also consider how you are lifting. Don't lift her by the front legs (eg like a child or a cat) -- this can be very painful for a dog as they do not have the flexibility of a cat. When you lift her, be sure you are fully supporting her, firmly and securely, across the chest and are holding up her hind legs. Don't leave her dangling, whch is also uncomfortable and even painful for some pups/dogs.
Also consider whether she may have been dropped at some point while being lifted or carried. An accident like this, maybe before you even got her, may make being carried a truly terrifying thing for her. And I'd not let children lift and carry her around at all. It is easy for small kids in particular to lift puppies incorrectly or worse, drop them from a height as they can squirm loose very unexpectedly. You don't want her to have even more negaive associations with being carried. It's always good practice to have kids sit on the fllor and lift and play with the puppy from that level rather than standing.
In short -- you want to make being carried a completely positive experience for her at all times, and one which she gets rewarded for.
The lunging is just her being playful -- normal puppy behaviour!
If you have a really hyper and active puppy, that is what you will have as an adult! This is the type of dog a lot of trainers would select out for agility. She will likely always need a lot of focused activity and brain activity too to keep her busy and thinking. I have a dog like this and he is a much loved challenge -- I find it very rewarding to have a really active, intensive dog like this --- BUT... thay ARE a handful and after four years it doesn't get any easier. :lol:
